Based on the results of randomized clinical trials (RCT) assessing direct oral anticoagulants (DOACs) for the treatment of patients with cancer-associated thrombosis (CAT), DOACs have been proposed as alternative to low molecular weight heparin by several international guidelines. However, the proportion of CAT patients who would have not been eligible for such trials is currently unknown.

Our primary aim was to assess the proportion of patients seen in clinical practice for acute CAT who would not have been eligible for CARAVAGGIO or HOKUSAI-VTE RCT. Secondary aim was to describe patients outcomes according to eligibility.

In a multicenter, observational study, all patients consecutively admitted from January 2017 to December 2019 for an acute CAT event were retrospectively analyzed. Patients were classified according to the presence or absence of non-inclusion criteria for CARAVAGGIO or HOKUSAI-VTE RCT. Event free survival during a 6-month follow-up were analyzed as secondary endpoints.

Among the 302 patients (women: 53 %, mean age: 67.9 ± 13.2) analyzed, 138 (46 %) for HOKUSAI-VTE cancer and 161 (53 %) for CARAVAGGIO met one or more non-inclusion criteria. Main criteria were upper limb and unsual site thrombosis (n = 63, 18.5 %), anemia/thrombopenia (n = 43, 14.2 %), brain tumors (n = 33, 10.9 %), ECOG PS >2 (n = 28, 9.3 %), severe renal failure (n = 16, 5.3 %).

At 6 months, the event-free survival rate was not statistically different between the two groups.

Almost half of CAT patients would have not been able to participate to a modern DOAC RCT. Evaluation of DOACs safety and efficacy in this subset of patients deserves further research.